Fabrication and Characterization of Cu(In,Ga)Se2 Solar Cells with Absorber Bandgap from 1.0 to 1.5 eV

Cu(InGa)Se2 films were deposited by selenization of Cu/Ga/In precursor layers and by four source elemental evaporation. Characterization of films and devices is presented. The selenized films show that the process results in two phase films and the devices behave like CuInSe2 devices. A high temperature anneal converts the films to single phase, resulting in an increased Voc. Th Ga and In areuniformly incorporated in the evaporated Cu(InGa)Se2 films and consequently Voc increases as the Ga content increases. However, the performance of the evaporated devices with high Ga are limited by voltage dependent current collection. The orientation of Mo and Cu(InGa)Se2 films are found to be related but in this case there is no correlation between the film characterization and device behavior. Cu(InGa)Se2 films with the relative orientation differing by two orders of magnitude give nearly identical device results.